CHAPTER 13 SERIAL INTERFACE CHANNEL 0
248
User’s Manual U11302EJ4V0UM
(9) Transfer start
Serial transfer is started by setting transfer data to serial I/O shift register 0 (SIO0) when the following
two conditions are satisfied.
• Serial interface channel 0 operation control bit (CSIE0) = 1
• Internal serial clock is stopped or SCK0 is at high level after 8-bit serial transfer.
Cautions 1.
If CSIE0 is set to “1” after data write to SIO0, transfer does not start.
2.
Because the N-ch open-drain output must be made to go into a high-impedance
state during data reception, write FFH to SIO0 in advance. However, when the
wakeup function specification bit (WUP) = 1, the N-ch open-drain output always
goes into a high-impedance state. Thus, it is not necessary to write FFH to SIO0.
3.
If data is written to SIO0 when the slave is busy, the data is not lost.
When the busy state is cleared and SB0 (or SB1) input is set to the high level
(READY) state, transfer starts.
Upon termination of 8-bit transfer, serial transfer automatically stops and the interrupt request flag (CSIIF0)
is set.
For the pin that is to be used for data I/O (SB0 or SB1), be sure to set as follows before serial transfer of the
1st byte after RESET input.
[1] Set the P25 and P26 output latches to 1.
[2] Set bit 0 (RELT) of the serial bus interface control register (SBIC) to 1.
[3] Reset the P25 and P26 output latches from 1 to 0.
(10) Judging busy status of slave
When the device is in the master mode, follow the procedure below to judge whether the slave device is in
the busy state or not.
[1] Detect acknowledge signal (ACK) or interrupt request signal generation.
[2] Set the port mode register PM25 (or PM26) of the SB0/P25 (or SB1/P26) pin to the input mode.
[3] Read out the pin state (when the pin level is high, the READY state is set).
After detection of the READY state, set the port mode register to 0 and return to the output mode.
(11) SBI mode precautions
(a) Slave selection/non-selection is detected by match detection of the slave address received after bus
release (RELD = 1).
For this match detection, the match interrupt (CSIIF0) of the address to be generated with WUP =
1 is normally used. Thus, execute selection/non-selection detection by slave address when WUP
= 1.
(b) When detecting selection/non-selection without the use of an interrupt with WUP = 0, do so by means
of transmission/reception of the command preset by program instead of using the address match
detection method.
(c) In SBI, after specifying reset of BUSY, the BUSY signal is output until the fall of the next serial clock
(SCK0). If WUP = 1 is set during this interval by mistake, it will be impossible to reset BUSY.
Therefore, after BUSY is released, make sure that the SB0 (SB1) pin is high level before setting WUP
= 1.
Содержание mPD780204
Страница 2: ...2 User s Manual U11302EJ4V0UM MEMO ...